Motion picture viewer with sound system

ABSTRACT

An adaptor, in the form of a modular base section, is provided for adding a major portion of a sound recording and reproduction system to a motion picture viewer. The adaptor base section mounting components, including a loudspeaker, of the sound system is adapted to be coupled to a main housing section of the viewer in place of a non-sound or standard base section. The components mounted in the adapter base section are advantageously arranged according to height so as not to intrude into an internal optical path within the viewer.

United States Patent [191 Hardy et a1.

1 1 Feb. 11, 1975 1 1 MOTION PICTURE VIEWER WITH SOUND SYSTEM [22] Filed: June 28, 1973 [21] Appl. No.: 374,640

[52] US. Cl. 352/34, 352/72, 352/104 [51] Int. Cl. G03b 31/02 [58] Field of Search 352/26, 27, 34, 35, 72, 352/104, 242; 353/15, 18, 74, 77, 78,119

[56] References Cited UNITED STATES PATENTS 2,513,673 7/1950 Prell 353/18 X 3,227,508 1/1966 Bavaro 353/18 X 3,310,360 3/1967 Jarvis et a1 352/242 3,344,709 10/1967 Taylor 353/78 X 3,357,303 12/1967 Staar 353/15 3,731,999 5/1973 Ventre 353/18 EFFECTIVE LENGTH OF BASE 96 3,733,121 5/1973 Smitzer 353/23 X 3,740,127 6/1973 Baker et a1. 352/72 3,779,634 12/1973 Kirchgessner 353/78 FOREIGN PATENTS OR APPLICATIONS 559,364 6/1958 Canada 352/34 1,128,287 4/1962 Germany Primary Examiner.lohn M. Horan Assistant Examiner-Alan Mathews Attorney, Agent, or Firm-John S. Vale 1 57] ABSTRACT An adaptor, in the form of a modular base section, is provided for adding a major portion of a sound recording and reproduction system to a motion picture viewer. The adaptor base section mounting components, including a loudspeaker, of the sound system is adapted to be coupled to a main housing section of the viewer in place of a non-sound or standard base section. The components mounted in the adapter base section are advantageously arranged according to height so as not to intrude into an internal optical path within the viewer.

2 Claims, 8 Drawing Figures SECTION 12 EFFECTIVE LENGTH OF BASE SECTION 16 SHEET 30F 5 PATENTEI] FEB I 1 I975 EFFECTIVE LENGTH OF BASE 96 SECTION l2 EFFECTIVE LENGTH OF BASE IFIG.5

VIEWER LOGIC 3.865.475 SHEET t UF 5 RECORD ERASE a -REPLAY CONTROL-A AU mo LO 0 IC MODE SELECTOR HEAD AND RECORD CAPSTAN osmou ERASE CONTROL-B REPLAY AMPLIFIER RECORDREPLAY ERASE SIGNAL FIG.'6

MOTION PICTURE VIEWER WITH SOUND SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of photography and, more particularly, to motion picture projectors or viewers of the type including sound reproduction systems.

2. Description of the Prior Art The present invention relates to apparatus for conveniently and relatively inexpensively adding a major portion of sound reproduction and/or recording system to a motion picture projector or viewer of the type disclosed in the copending applications of Edwin H. Land, Ser. No. 318,513, filed on Dec. 26, 1972, now US. Pat. No. 3,822,934, and Ser. No. 227,080 (now abandoned), filed on Feb. 17, 1972, both of which are assigned to the same assignee as the present invention.

In a preferred embodiment, the viewer is configured to receive a multi-purpose film handling cassette including a self-developing film strip and a processing station for treating the film strip with a liquid processing composition to initiate a diffusion transfer process. Examples of such cassettes may be found in both of the above-noted copending applications.

In use, the film handling cassette is mounted in an appropriate camera to expose the film strip. The cassette is then transferred to the viewer wherein the film strip is automatically processed and shortly thereafter projected on a rear projection screen forming an integral part of the viewer. Subsequent to projection, the film strip is automatically rewound and the cassette is ejected from the viewer. On the next insertion of the cassette into the viewer, the viewer senses that the film strip has already been processed and it automatically proceeds through a projection, rewind, and-ejection cycle.

There are presently many projectors and viewers on market which have optical or magnetic sound reproduction systems. These projections or viewers are specially designed to include a sound capability and generally are much larger and bear little physical resemblance to their counterpart projectors or viewer without such a sound capability. One such sound viewer is disclosed in US. Pat. No. 3,702,721, issued to I. M. Skuja on Nov. 14, 1972.

SUMMARY OF THE INVENTION The present invention provides an adaptor for adding a major portion of a sound recording and reproduction system to a viewer of the type disclosed in the previously mentioned copending applications. More specifically, the adaptor takes the form of a modular base section, mounting components of the sound system, which may be coupled to a main housing section of the viewer in place of a standard base section.

Advantageously, the adaptor is not much larger than the standard base section, thereby allowing the addition of a sound system to the viewer without significantly increasing the overall dimensions of the viewer. Also, because of the interchangeability of the adaptor base and the standard base, significant manufacturing cost savings may be realized.

The standard viewer includes a main housing section formed in part by a rear projection screen. Coupled to and supporting the main housing section is a standard hollow base section. The viewer also includes means for receiving a cassette holding a film strip; projection means for directing light, bearing images from the film strip, towards the base section; and reflecting means in the base section for reflecting the image-bearing light along an upwardly inclined optical path to the rear of the rear projection screen.

The adaptor apparatus comprises a second hollow base section that is highly longer than the standard base section and is configured to be coupled to the main housing section in place of the standard base section. The increase in length provides space in the forward portion of the second base section beneath the rear projection screen for mounting a loudspeaker forming part of the sound reproduction.

It was noted earlier that the reflecting means mounted in the standard base section is adapted to reflect the image-bearing light upwardly from the base section along an inclined path to the rear projection screen. The second base section also includes means for mounting reflecting means or a mirror in the same predetermined spacial relationship with the projection means and the rear projection screen, thereby maintaining the same inclined optical path.

In order to minimize the size of the sound viewer, electrical and electronic components forming such elements of the system as a record and playback amplifier are mounted in the second base section in the heretofore unoccupied space between the lower edge of the inclined optical path and a bottom wall of the base section. These electronic components are advantageously arranged in ascending order of height so as not to intrude into the upwardly inclined optical path.

The rear projection screen and mirror are disposed at different acuteangles relative to the bottom wall of the second base section. The viewer also includes internal baffle plates or shields which cooperate with the rear projection screen, mirror and the base section to define an irregular shaped chamber having non-parallel walls. The primary purpose of this chamber is to enclose and light shield the inclined optical path. However, by positioning the loudspeaker inthe forward end of the adaptor base section, this same chamber is used to improve the audio quality of the speaker output by providing an environment which discourages the formation of standing audio waves. This provides an economic advantage in that little or no sound absorbing material has to be provided within the main housing section for the speaker.

Therefore, it is an object of the present invention to provide a simple and relatively inexpensive adaptor for adding a major portion of a sound system to a motion picture viewer.

It is another object of the invention to selectively arrange components of the sound system within the viewer to take advantage of heretofore unused space and thereby minimize the increase in size of the viewer when adding such a sound capability.

It is yet another object of the invention to utilize an existing optical chamber within the viewer to significantly improve the performance of the sound system by using the chamber as an audio chamber for a loudspeaker forming part of the sound system.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS j viewer having a standard or non-sound base section coupled thereto;

FIG. 4 is a side elevational view of the motion picture I a viewer embodying the instant invention showing the audio adaptor base section coupled to the main housing section;

FIG. 5 is a front elevational view of the audio adaptor base section shown in FIGS. 1 and 4;

FIG. 6 is a diagrammatic representation of a sound system for a motion picture viewer embodying the instant invention;

FIG. 7 is a perspective view of a motion picture viewer having a standard or non-sound base section; and

FIG. 8 is a perspective view of a motion picture viewer having an audio adaptor base section.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention provides apparatus for adapting or converting a standard or non-sound version of a motion picture viewer shown in FIGS. 3 and 7 of the drawings to a viewer having a sound capability as shown in FIGS. 1, 4 and 8. More specifically, the invention provides an audio adaptor base section which is adapted to be interchanged or substituted for a standard or non-sound base for easily and economically adding a major portion of a sound system to the viewer without significantly increasing its overall dimensions.

As best shown in FIGS. 3 and 7, the non-sound version of the viewer (designated 10A) includes a first hollow base section 12 and an upper main housing section 14 coupled to and supported by base section 12.

The sound version of the viewer (designated 10B) shown in FIGS. 1, 4 and 8 includes substantially the same main housing section 14 mounted on an audio adaptor base section or second hollow base section 16.

The standard or non-sound viewer 10A will be described first. The main housing section 14 is a box-like structure which is formed in part by a rear projection screen 18 and houses the operating mechanisms of the viewer. It includes a top horizontal wall 20; a pair of spaced vertical side walls 22; a rear wall 24 including an upper vertical section 24a and a lower inwardly sloping section 2412; and a forward wall 26 inclined rearwardly from the vertical and mounting the rear projection 18. The bottom of housing section 14 facing the base section 12 is open.

The top wall 20 has a pivotally coupled door 28 which covers an elongated slot (not shown) providing access for loading a film handling cassette 30 (see FIG. 2) into a vertically depending receiving chamber (not shown) to locate cassette 30 at an'operative position within the viewer 10A as shown in FIG. 3.

Cassette 30 includes a parallelepiped shaped housing 32 enclosing supply and take-up reels (not shown) having a length of photographic film strip 34 coupled therebetween. Access to the film strip for exposure and projection purposes is provided by an opening 36 in a bottom peripheral wall 38 of cassette 30.

The film strip is preferably of the self-developing" type disclosed in U.S. Pat. Nos. 2,726,154 or 2,944,894.

The cassette 30 is adapted to be loaded in a suitable camera for exposing film strip 34. Subsequent to exposure, the cassette is transferred to the viewer 10A receiving chamber. Upon initial insertion of the cassette 30, mechanisms (not shown) within housing section 14 automatically (1) sense that the film strip 34 has not been processed; (2) activate a processing station (not shown) within the cassette 30; (3) rewind the film strip 34 past the processing station where the filmstrip 34 is treated with a liquid processing composition to initiate a diffusion transfer process; (4) advance the developed film forward past opening 36 for projection; (5) rewind the film strip 34 after projection; and (6) eject the cassette from the receiving chamber. Upon the next insertion of the cassette 30 into the viewer 10A, a sensing mechanism senses that the film strip 34 has already been processed and the viewer automatically bypasses the processing mode of operation and proceeds directly to a projection, rewind and eject cycle.

Viewer 10A includes projection means which is diagrammatically illustrated as a projection lens 40 positioned at the bottom of the receiving chamber so as to be in alignment with opening 36 in cassette 30. The projection means also includes a light source (not shown) for illuminating that portion of the film strip 34 at opening 36 through a prism (not shown) mounted in cassette 30.

The image-bearing light is projected by lens 40 towards the base section 12. Mounted in base section 12 is an inclined reflecting means or mirror 42 which directs the light to the rear of rear projection screen 18.

Base section 12 is an open top hollow structure which is adapted to be coupled to the bottom of main housing section 14. It is formed by a generally rectangular bottom wall 44, a pair of spaced elongated side walls 46, a leading end wall 48 formed by an upper inclined section 48A and a lower inclined section 48B, and a trailing end wall 50. 5 Mirror 42 is supported by a suitable mirror support member 52 mounted on bottom wall 44 of base section 12. Member 52 is adapted to support mirror 42 in a predetermined spacial relationship with the projection lens 40 and the rear of rear projection screen to establish an appropriate folded optical path from the lens 40' to rear projection screen 18 so that the projected images fill the entire screen 18 and are in sharp focus.

The folded optical path (shown in dotted lines in FIG. 3) includes a first representative center light ray 54 from the lens 40 to mirror 42 and a second representative center light ray 56 from the mirror 42 to the rear of screen 18. Light ray 54 is projected from lens 40 towards base section 12 in a direction substantially normal to bottom wall 44 until it impinges mirror 42 supported at a predetermined acute angle A with respect to bottom wall 44. Mirror 42 reflects the light along an upwardly inclined optical path, represented by center light ray 56, at a predetermined acute angle B with respect to bottom wall 44.

While the optical path from mirror 42 to screen 18 has been diagrammatically illustrated by a single representative center light ray 56, in actuality, the light projected by lens 40 and reflected mirror 42 comprises an expanding cone or bundle or light rays. The bounds of the inclined optical path are therefore indicated by dotted lines 56a and 56b which are intended to represent upper and lower edge rays, respectively, of the cone of light.

It will be noted in FIG. 3 that the lower portion of mirror 42 is located in base section 12 and the upper portion of the mirror is located in main housing section 14. A door 57 is preferably located in bottom wall 44 of base section 12 to provide access for cleaning and adjusting mirror 42 and lens 40. The line of demarcation between base section 12 and main housing section 14 is shown by horizontal line 58.

Thus, the lower portion ofthe cone of light bounded by lower edge ray 56b travels from mirror 42 forwardly through a specified length of hollow housing section 12 then it crosses line of demarcation 58 at point 60 into main housing section 14 to impinge upon screen 18.

When reference is made to the length of base section 12, it will be understood that this dimension is the distance between leading end wall 48 and trailing end wall 50. The width is measured between side walls 46, and the height is measured between bottom wall 44 and the line of demarcation 58 between base section 12 and main housing section 14.

While the length of base section 12 forwardly from the mirror 42 to the point of ray 56b cross over 60 must be of a predetermined distance, the leading end wall 48 does not have to be located much to the left of point 60 (as viewed in FIG. 3). In the illustrated embodiment, the leading end wall 48 is shown to include upper and lower inclined sections 48a and 48b. This type of wall structure is provided for styling or aesthetic reasons.

For the purposes of this disclosure, it will be understood that leading end wall 48 could be located at dotted vertical line 62 and that in viewer A the rear projection screen 18 extends forwardly (to the left in FIG. 3) of the leading end wall of base section 12. Discounting the styling considerations of leading end wall sections 48a and 48b, the effective length of base section 12 will be considered to be the distance between the trailing end wall 50 and the vertical dotted line 62.

Although not shown in the drawings, side walls 46 of base section 12 and side walls 22 of main housing section 14 preferably include complementary and abutting horizontal flanges having pre-registered drilled and tapped holes for receiving screws for coupling base section 12 to main housing section 14.

Main housing section 14 is also provided with means for light shielding the optical path 56 from mirror 42 to rear projection screen 18. In a preferred embodiment, the light shield is formed in part by cooperating baffle plates 64, 66 and 68 shown in FIG. 1. These three baffle plates define three sides of a light excluding tunnel from mirror 42 to the rear of screen 18. The fourth side of the tunnel is formed by the hollow base section 12 in viewer 10A.

It will be noted that plates 64, 66 and 68 are disposed in non-parallel relationship to one another so that the cross section of the tunnel expands along the length of the tunnel from the mirror 42 to the screen 18 to accommodate the expand cone of image-bearing light. Top plate 66 includes an opening 70 near its trailing end through which the image-bearing light is transmitted along optical path 54 from projection lens 40 to mirror 42.

Since cassette 30 and film strip transport and projecting mechanisms in main housing section 14 do not form any part of the present invention, they have only been described to the extent necessary to provide adequate background information. Detailed descriptions of a representative cassette 30 and the standard or nonsound viewer 10A may be found in copending applications of Edwin H. Land, Ser. No. 318,513, filed on Dec. 26, 1972, and Ser. No. 227,080, filed on Feb. l7, l972, both of which are assigned to the same assignee as the present invention.

In a preferred embodiment, viewer 10A is adapted to be converted to the sound version of the viewer 10B by the addition of a magnetic sound recording and reproduction system of the general type shown in block diagram form in FIG. 6.

In a sound version of cassette 30 shown in FIG. 2, the film strip 34 includes conventional sprocket holes 72 along one edge of the film strip for engagement with claw drive mechanisms in the camera and viewer. Along the opposite edge of the film strip, outside of the image-forming area, is an outwardly facing magnetic sound recording track or strip 74. Access to the magnetic strip 74 for a recording and playback head is provided by an opening 76 in an end peripheral wall 78 of cassette 30. A second opening 80 is provided in wall 78 for a capstan drive unit which is utilized to drive that portion of film strip 34 in alignment with opening 76 past the recording/playback head in a continuous manner in contrast to the intermittent movement of portions of the film strip 34 being moved past-the exposure/projection opening 36 in wall 38 by the claw drive mechanism.

As shown in FIG. 6, the sound system, which is intended to be representative of a general type, includes an electronic Audio Logic system which is connected to a Viewer Logic system that controls the automatic processing/projection/eject cycle. The Viewer Logic serves as a first input to the Audio Logic for coordinating the operation of the sound system with operating cycle of the viewer.

A second input to the Audio Logic is provided by Record/Erase/Replay Control-A which includes a microphone 82. Control-A is an auxiliary unit that is adapted to be plugged into the viewer through a connector 84 so that the user may control the sound system from a location remote from the viewer. Using Control-A, the user may command the sound system, through the Audio Logic, to record a signal on magnetic track 74, erase a recorded signal, or play a recorded signal.

The Audio Logic has two outputs. The first serves as an input to an electro-mechanical Head and Capstan Position Control-B which functions to move a recordlreplay head 86 and a capstan drive unit 88 into and out of operative engagement with the film strip 34 through openings 76 and 80 in cassette 30, respectively.

Head 86 and capstan drive unit 88 are shown mounted on an arm 90 which is pivotally near its lower end on a pin 92. Control-B functions to pivot arm 90 in a counter-clockwise direction about pin 92 to move head 86 and capstan 88 into operative engagement with film strip 34. To move head 86 and capstan 88 out of operative engagement with film strip 34, Control-B pivots arm 90 in a clockwise direction.

The second output of the Audio Logic serves as an input for the Mode Selector which in turn has an output serving as an input for an Amplifier and Erase Signal system. The Amplifier and Erase Signal system is connected between the record/replay head 86 and a speaker 94.

In operation, the cassette 30 is placed in a viewer and during a projection cycle, and the user, while looking at the images on the screen 18, uses Control-A to initiate a record mode of operation and speaks into microphone 82 to record a narrative on magnetic track 74. In the record mode, Control-A, the Audio Logic, and the Mode Selector connect the record/replay amplifier between microphone 82 and record/playback head 86 to record the signal on magnetic track 74.

To initiate an audio replay mode of operation, the user employs Control-A to instruct the cooperating Audio Logic and Mode Selector to couple the record/- playback amplifier between the record/replay head 86 and the loudspeaker 94.

The Amplifier and Erase Signal system includes a high frequency oscillator for providing a magnetic erase signal. Again, the user may initiate an erase cycle by utilizing Control-A to command the Audio Logic and Mode Selector to cause the high frequency erase signal to be transmitted to head 86.

The preceding brief outline of the sound system is provided as background information in preparation to describe the audio adaptor base section 16. For a more detailed description of the sound system, reference may be had to copending application Ser. No. 374,639 filed on even date herewith and being assigned to the same assignee as the present invention.

As noted earlier, a major portion of the sound system diagrammatically illustrated in FIG. 6 may be added to .the viewer by substituting the audio adaptor base'section 16 for the standard base section 12.

As best shown in FIGS. 1, 4 and 8, the audio adaptor base section 16, or the second hollow base section, comprises an open top shell-like structure formed by a generally rectangular, planar bottom wall 96 and four upstanding peripheral walls including a pair of spaced side walls 98, a trailing end wall 100, and a leading end wall 102.

The length of base section 16 is the distance between leading end wall 102 and trailing end wall 100. The height is the vertical distance from bottom wall 96 to the top of the peripheral walls 98, 100 and 102, and the width is measured between the side walls 98.

Dimensionally, the height and width of base section 16 is preferably the same as the corresponding dimensions of the standard base section 12. The length, however, of base section 16 is greater or longer than that of base section 12.

As best shown by comparing FIG. 3 with FIg. 4 and FIG. 7 with FIG. 8, the increase in length is at the leading end of the base section 16. It will be noted in FIG. 7 that the lower portion of rear projection screen 18 extends forwardly of the leading end of base section 12 while in FIG. 8 the increased forward length of base section 16 eliminates such an overhang.

. In FIG. 4 the effective length of base section 12 is graphically compared to the effective length of base section 16 to show a forward length differential X. The

term effective length means the utilized or useful length of these base'sections discounting the inclination of leading and trailing end walls for styling purposes.

Referring to FIG. 4, it will be seen that audio adaptor base section includes means for supporting the mirror 42 in the form of a mirror mount or support member 104 mounted on bottom wall 96. Support member 104 is identical in construction to the mirror support member 52 used in the standard base section 12 and it supports mirror 42 at the same angle A with respect to bottom wall 96. Thus, when base section 16 is coupled to main housing section 14, support member 104 supports mirror 42 in the same predetermined spacial relation with respect to projection lens 40 and the rear projection screen 18 to establish the same optical path 54 from lens 40 to mirror 42 and the same optical path 56 from mirror 42 to rear projection screen 18. Again, center ray 56 is inclined upwardly at the same acute angle B with respect to bottom wall 96 and the expanding cone of light is bounded by upper and lower edge rays 56a and 56b. The lower edge ray 56b is inclined upwardly at an acute angle C with respect to bottom wall 96, angle C being smaller than acute angle A. It will be noted that the vertical height or distance from the interior surface of bottom wall 96 to the lower edge ray 56b is at a minimum at mirror 42 and that height increase above the minimum in a substantially linear manner until it reaches a maximum height or distance at rear projection screen 18.

As best shown in FIGS. 1, 4 and 5, theopen space between the inclined lower edge ray 56b and bottom wall 96 is used to house a major portion of the sound system shown in FIG. 6.

The largest single component of the sound system, in terms of physical size, is the loudspeaker 94. It is positioned in the leading end of hollow base section 16 facing the leading end wall 102 which has a plurality of elongated horizontal slots or openings 106 therein to allow the transmission of audio waves therethrough. In a preferred embodiment, an open weave cloth cover may be positioned on the interior surface of leading end wall 102 in covering relation to slots '106 for aesthetic reasons. It will be noted that the cone portion 108 of speaker 94 is oval in shape so that it conveniently. fits the space between the bottom wall 96 of base section 16 and the leading end of the lower edge light ray 56b without intruding into the optical path 50 between mirror 42 and rear projection screen 18.

Positioned behind speaker 94 is a generally planar L-shaped circuit board 110 mounted on bottom wall 96. A forward portion of circuit board 110 extends substantially across the width of base section 16 from the trailing end of speaker 94 to a point in front of a door 111 in bottom wall 96 which is identical to the door 57 in base section 12 and serves to provide access for cleaning and/or adjusting mirror 42 and projection lens 40. A rearward portion of the circuit board 110 extends along the right side of base section 16 (as viewed in FIG. 1) between door 111 and the right side wall 98.

Mounted on the circuit board 110 are a plurality of discrete electrical and electronic components which are electrically interconnected to form the previously described Amplifier and Erase Signal system and the Mode Selector. Speaker 94 is connected to the output of the amplifier and a suitable interconnected cable 112 is provided for interconnecting the Mode Selector with the Audio Logic which will be mounted in main housing section 14 along with the Viewer Logic, the record/replay head 86, capstan drive 88 and Control B.

The record and replay amplifier, high frequency erase signal oscillator or generator and mode selector maybe of the types which are well known to those skilled in the electrical and magnetic recording arts and will not be described since they do not form any part of the present invention.

The present invention is directed specifically to the unique arrangement of the plurality of electrical and electronic components within base section 16 so that they do not intrude into the optical path between mirror 42 and rear projection screen.

As best shown in FIGS. 1 and 4, the electrical and electronic components vary in vertical height. For example, small resistors 114 and small capacitors 116 are not as tall as the minimum distance from bottom wall 96 to the lower edge ray 56b at mirror 42. Other components such as speaker 94, a high frequency oscillator 118, large capacitors 122, medium capacitor 120, etc., are of a height which is intermediate to the minimum distance from lower edge ray 56b to bottom wall 96 at mirror 42 and the maximum distance from lower edge ray 56b to bottom wall 96 at screen 18.

As best shown in FIG. 4, the electronic and electrical components are advantageously arranged in descending order of height on circuit board along the length of base section 16 from leading end wall 102 towards trailing end wall 100 so that none of the components intruded into the optical path between mirror 42 and the rear projection screen. Stated another way, these components are disposed in ascending height along the length of base section 16 in a direction from trailing end wall 100 towards leading end wall 102.

For example, the small capacitors 116 and small resistors 114 are mainly located nearer trailing end wall 102. Going forwardly, in ascending order of height, are capacitors 120 and 122, oscillator 118 and speaker 94.

It is to be understood that the arrangement of componentsshown in the drawings is intended to be illustrative of the concept of arranging the components according to height to make full utilization of the heretofore unused space between the bottom wall of the base section and the lower edge of the optical path between mirror 42 and screen 18. The specific components may be arranged in any other order in relation to one another as long as none of them intrudes into the optical path.

As best shown in FIGS. 1 and 8 the audio system includes a volume control or potentiometer 124 preferably mounted at the leading end of circuit board 110 to the right of speaker 94 (as viewed in FIG. 1). Volume control 124 includes a rotatable shaft 126 which extends through leading end wall and supports a knob 128 on its exterior end which the user may employ to manually adjust the volume of the sound system.

Mounted on the opposite side of speaker 94 and extending through an opening in leading end wall 102 is the female portion of connector 84 which is appropriately connected to cable 1 12. As best shown in FIG. 8, Control-A is shown to include a control box 130, the microphone 82, and a cable 132 having the male portion of connector 84, at one end, which is adapted to be plugged into the female portion 84 to connect Control-A to the Audio Logic through cable 112.

In terms of physical size, the Amplifier Erase Signal system, the speaker 94, and the Mode Selector are the largest elements of the sound system and they are housed, by the unique arrangement of their individual components according to height, within the hollow audio adaptor base section 16. Control-A is an external element that is not mounted in viewer 10b but adapted to be connected to the sound system via connector 84. This leaves the Audio Logic and Control B which are relatively small and may be mounted in heretofore unused spaces in main housing section 14.

As best shown in FIG. 4, the head 86, and capstan drive 88 and pivot arm 90 may be mounted in a space between the rear wall portion 24a and the end peripheral wall 78 of the cassette 30 located at its operative position within viewer 10b. The relatively small Viewer Logic, Audio Logic and Control B may be mounted in a space below cassette 30 and pivot arm 90 or some other suitable unoccupied space in main housing section 14. As indicated earlier, the three baffle plates 64, 66, 68, and base section 16 form a tunnel having an expanding cross section for enclosing and light shielding the optical path 56 from mirror 42 to rear projection screen 18. At one end of the tunnel, mirror 42 is supported at an acute angle A with respect to base section bottom wall 96. At the opposite end, rear projection screen 18 is disposed at an acute angle D with respect to bottom wall; angle D being larger than angle A.

The baffle plates 64, 66, 68; base section 16 in general and bottom wall 96 in particular; mirror 42; and rear projection screen 18 cooperate to form nonparallel walls defining an irregular shaped optical chamber 134. Advantageously, by mounting loudspeaker 94 at the leading end of base section 16 not only is the speaker facing in the same direction as screen 18 so that the sound is directed towards the audience viewing the screen 18, but the optical chamber 134 now serves as an acoustical chamber for speaker 94.

It is well known in the audio art that the vibrating cone ofa loudspeaker emits directional sound or audio waves in both a forwardly and rearwardly direction. If the speaker is mounted in a box or enclosure, it is desirable to provide some means for absorbing the back or rearwardly directed waves so that they do not interfer with the forwardly directed waves. Usually some type of sound absorbing material is provided in the enclosure. Of particular concern is the undesirable formation of standing back waves in the enclosure which is caused by a resonance effect relating to the length of certain parallel walls of the enclosure. Such standing back waves in the enclosure inhibit the free translational movement of the speaker cone 108 and thereby degrade the quality of the audio output from the speaker 94.

It will be noted that the chamber defined by the baffle plates 64, 66, and 68, screen 18, mirror 42, and bottom certain frequency audio waves and the physical dimensions between parallel wall 96 has non-parallel walls and therefore an irregular shape. Thus, the chamber 134 provides an environment for speaker 94 which discourages the formation of standing back waves by providing an enclosure with non-parallel walls that tend to inhibit the formation of such standing waves thereby enhancing the audio performance of speaker 94.

In a preferred embodiment, the main housing section 14 and the audio adaptor base section 16 include horizontal abutting flanges (not shown) associated with their respective side walls 22 and 98 providing mating surfaces for coupling section 14 to section 16. Preferably these flanges include appropriately drilled and tapped holes for receiving coupling screws. Since base sections 12 and 16 are adapted to be interchangeable, the mounting holes in the flanges of base sections 12 and 16 are disposed to match the corresponding mounting holes in the flanges on main housing section 14.

in summary, an audio adaptor base section has been provided which is configured to be interchanged with a standard base section of a motion picture viewer to add a major portion of a sound system to the viewer.

The audio adaptor base section includes electronic and electrical components mounted therein according to their relative heights to insure such components do not intrude into an inclined optical path within the viewer. Also a speaker, forming part of the sound system, is advantageously mounted within an irregular shaped optical chamber to enhance the audio performance of the sound system.

Since certain changes may be made in the above apparatus without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

We claim: 1. A motion picture viewer system that is convertible from an image projection mode of operation to an image projection and sound reproduction mode of operation, said viewer system comprising:

a main housing section formed in part by a rear projection screen and including an open bottom;

projection means in said main housing section for projecting image-bearing light towards said open bottom of said main housing section;

a first hollow base section locatable in closing relation with said open bottom when said viewer is operable in the image projection mode of operation, said first base section having a given length between leading and trailing ends thereof and being dimensioned so that said rear projection screen extends forwardly of said leading end of said base section by a predetermined distance, said first base section further including first means for mounting reflecting means in a predetermined spacial relationship with said projection means and said rear projection screen for reflecting the image-bearing light onto the rear of said rear projection screen; a second hollow base section loctable in closing relation with said open bottom of said main housing in place of said first base section when said viewer is operable in the image projection and sound reproduction mode of operation, said second base section being longer between leading and trailing ends thereof than the given length of said first base section such that the distance between said rear projection screen and said leading end of said second base section is smaller than the predetermined distance between said rear projection screen and said leading end of said first base section, said second base section including second means for mounting reflecting means in the same predetermined spacial relationship with said projection means and said rear projection screen as when said first base section is located in operative closing relation with said open bottom of said main housing section; and a portion of a sound system including a loud speaker mounted in said second base section, said loud speaker being positioned adjacent said leading end of said second base section and occupying a space in said second base section attributable to the greater length of said second base section as compared to said first base section. 2. A motion picture viewer system as defined in claim 1 wherein said second base section includes a bottom wall and said second mounting means is configured to mount the reflecting means over said bottom wall near said trailing end of said second base section in position to reflect the image-bearing light along an inclined optical path to the rear of said rear projection screen, said optical path being inclined upwardly from said bottom wall and being a minimum distance from said bottom wall at the reflecting means and a maximum distance greater than said minimum distance from said bottom wall at said rear projection screen, said portion of said sound system including a plurality of electrical and electronic components of varying height, some of said components being of a height smaller than said minimum distance and other of said components being of a height between said minimum and maximum distances, said component being mounted on said bottom wall in ascending order of height between the reflecting means and the rear projection screen so that none of said plurality of components intrudes into said inclined optical path. 

1. A motion picture viewer system that is convertible from an image projection mode of operation to an image projection and sound reproduction mode of operation, said viewer system comprising: a main housing section formed in part by a rear projection screen and including an open bottom; projection means in said main housing section for projecting image-bearing light towards said open bottom of said main housing section; a first hollow base section locatable in closing relation with said open bottom when said viewer is operable in the image projection mode of operation, said first base section having a given length between leading and trailing ends thereof and being dimensioned so that said rear projection screen extends forwardly of said leading end of said base section by a predetermined distance, said first base section further including first means for mounting reflecting means in a predetermined spacial relationship with said projection means and said rear projection screen for reflecting the imagebearing light onto the rear of said rear projection screen; a second hollow base section loctable in closing relation with said open bottom of said main housing in place of said first base section when said viewer is operable in the image projection and sound reproduction mode of operation, said second base section being longer between leading and trailing ends thereof than the given length of said first base section such that the distance between said rear projection screen and said leading end of said second base section is smaller than the predetermined distance between said rear projection screen and said leading end of said first base section, said second base section including second means for mounting reflecting means in the same predetermined spacial relationship with said projection means and said rear projection screen as when said first base section is located in operative closing relation with said open bottom of said main housing section; and a portion of a sound system including a loud speaker mounted in said second base section, said loud speaker being positioned adjacent said leading end of said second base section and occupying a space in said second base section attributable to the greater length of said second base section as compared to said first base section.
 2. A motion picture viewer system as defined in claim 1 wherein said second base section includes a bottom wall and said second mounting means is configured to mount the reflecting means over said bottom wall near said trailing end of said second base section in position to reflect the image-bearing light along an inclined optical path to the rear of said rear projection screen, said optical path being inclined upwardly from said bottom wall and being a minimum distance from said bottom wall at the reflecting means and a maximum distance greater than said minimum distance from said bottom wall at said rear projection screen, said portion of Said sound system including a plurality of electrical and electronic components of varying height, some of said components being of a height smaller than said minimum distance and other of said components being of a height between said minimum and maximum distances, said component being mounted on said bottom wall in ascending order of height between the reflecting means and the rear projection screen so that none of said plurality of components intrudes into said inclined optical path. 